Circle protractor



g May 3, 1960 F. R. CURTIS 2,934,828 CIRCLE PROTRACTOR Filed Sept. 5. 195a f /G-j 0 5 M 6 INVENTOR.

CIRCLE PROTRACTOR Fay R. Curtis, Prairie du Chien, Wis.

Application September 5, 1958, Serial No. 759,335

1 Claim. (Cl. 33-75) This invention relates to a measuring and ruling instrument, and it particularly relates to a circular protractor device.

Although there are a great many different types of protractors in use today, they generally have one or another defect which makes them less than perfect. One common defect is that they are usually only semicircular in structure so that the instruments must be manipulated to obtain oppositely-extending measurements. On the other hand, if the instrument is circular, it is usually of such complex and expensive construction as to be economically infeasible.

It is one object of the present invention to provide a circular protractor which can be used to measure all angles with a minimum of manipulation.

Another object of the present invention is to provide a circular protractor which is simple in construction and easy to use.

Other objects of the present invention are to provide an improved protractor, of the character described, that is easily and economically produced, which is sturdy in construction, and which is highly eflicient in operation.

With the above and related objects in view, this invention consists in the details of construction and combination of parts, as will be more fully understood from the following description, when read in conjunction with the accompanying drawing in which:

Fig. 1 is a front elevational view of a protractor embodying the present invention.

Fig. 2 is a sectional view taken on line 22-of Fig. 1.

Fig. 3 is a sectional view taken on line 3-3 of Fig. 1.

Fig. 4 is an enlarged, detailed, fragmentary view of a portion of the protractor shown in Fig. 1.

Referring in greater detail to the drawing wherein similar reference characters refer to similar parts, there is shown a protractor, generally designated 10, which comprises a ring 12, preferably constructed of cast metal or the like. This ring 12 is provided with a circular scale 14 on one or both faces; this scale being divided into four quarters, ninety degrees in each quarter.

The ring 12 is provided with a peripheral flange 16 which extends perpendicularly in two opposite directions from the plane of the ring 16.

Extending across the diameter of the ring 12 is a bar '18, preferably constructed of hardwood. This bar 18 has one edge 19 extending from on one side of the ring 12 to 0 on the other side and is fixed to the ring at each of these 0 areas by screws or the like indicated at 20. These screws 20 pass through the ring 12 and through end portions 22 at each end of the bar 18. These end portions 22 are each separated from the 6 major portion of bar 18 by a recess 24.

2,934,828 Patented May 3, 1960 Also extending across the diameter of ring 12 and having its edge 25 coinciding with a diameter of ring 12 is a movable bar 26, also preferably constructed of hardwood. This bar 26 is provided with an undercut portion 28 at each end; these undercut portions 28 being slidably engaged in surface-to-surface contact with the top surface of the ring 12.

The bar 26 is adjustably and releasably connected to the ring 12 by means of a bolt 30 at each end adjacent the corresponding undercut portions 28. The bolts 30 are each provided with an enlarged portion 32 fitting in a corresponding opening in the bar 26. The enlarged bolt portions 32 are each provided with a flat head portion 34, and these head portions 34 are adapted to slidably pass through the recesses 24 of the bar 18 when the bar 26 is rotated to pass over the bar 18. A wing nut 36 is provided on each bolt 30 to releasably clamp the bar 26 against the ring 12 (as shown in Fig. 3).

In operation, by placing the protractor 10 with the edge 19 of the bar 18 along any straight edge or board edge, or the like, the protractor is set in position. The edge 25 of the bar 26 is then adjusted to the desired angle as indicated on the scale 14, after first loosening nuts 36; and after the bar 26 has been so adjusted, the nuts 36 are tightened to hold the bar 26 in its adjusted position. The bar 26 is then used as a rule to draw the desired angle.

Although this invention has been described in considcrable detail, such description is intended as being illustrative rather than limiting, since the invention may be variously embodied, and the scope of the invention is to be determined as claimed.

Having thus set forth and disclosed the nature of this invention, what is claimed is:

' An angle measuring and ruling protractor comprising a ring having oppositely disposed flat surfaces, a fixed =bar having a straight edge extending across the median diameter of said ring and having its opposite ends connected to said ring in surface-to-surface contact with one of said flat surfaces, a movable ruling bar having a straight edge extending across the diameter of said ring and having an undercut surface at each end, said undercut surfaces being in surface-to-surface slidable contact with the other of said flat surfaces, a bolt and nut assembly on each end portion of said movable ruling bar for releasably clamping said movable ruling bar to said ring, a recess in each end portion of said fixed bar to permit passage thereacross of said bolt and nut assemblies, a circular scale being provided on at least one of said flat surfaces of said ring, the opposite end portions of said movable bar extending across said scale on one surface of said ring in slidable contact therewith, said bolt and nut assemblies each comprising a bolt extending through the movable bar adjacent the corresponding undercut surface, a head on said bolt of a shape and size to slidably fit in said recesses in said fixed bar and to extend in overlapping clamping relationship over the opposite surface of said ring, and a wing nut on said bolt.

References Cited in the file of this patent UNITED STATES PATENTS 

